In general, when extruding a billet made of a metal material, for example, a material of aluminum or its alloy etc. by an extrusion press, a stem is attached to a front end of a main ram driven by a hydraulic cylinder, a container is pushed against the die, and, in that state, the billet on the billet loader is pushed by the stem of the front end of the main ram to fill it into the billet holding part of the container. Further, by making the main rain advance by further drive of the hydraulic cylinder, the billet is strongly pushed by the stem. Therefore, a shaped product is pushed out from the outlet of the die.
In this conventional type extrusion press, when loading a billet in the container, the front end of the stem must be retracted by the amount of the length of this billet. The stroke of the main ram becomes the billet length plus the length of the stem. Therefore, to secure the stroke of this main ram, the conventional type extrusion press ends up becoming larger as a whole. The hydraulic cylinder driving the main ram also becomes enlarged. Along with this, the amount of oil used for the working process has to be increased.
In recent years, extrusion presses are being made more compact. Due to this increasing compactness, space spacing and energy saving can be achieved in extrusion presses. An extrusion press called a “short stroke press system”, one technique for increasing the compactness, is being developed. In a conventional type of extrusion press, space for supply of the billet is required for loading the billet into the container. The stroke of the main ram became longer by exactly this amount of length. Therefore, in this short stroke press system, the method of supplying the billet is specially designed so as to shorten the length of the main stroke by exactly the amount of length of the space for billet supply.
According to this short stroke press system, the extrusion press as a whole can be made shorter in length and more compact, the nonextrusion time (idling time) can be shortened, and, furthermore, the amount of working oil of the hydraulic cylinder for driving the main ram can be reduced. As a result, space saving and energy saving of the extrusion press can be achieved.
This short stroke press system is divided into two types by the direction of supply of the billet with reference to the container. One system is a short stroke press system called the “front loading type”. This front loading type makes the container move to the stem side at the time of supplying a billet and thereby secures space for the supply of the billet at the die side due to the position of the container after movement. That is, the billet is supplied between the die and the front end of the stem.
In this front loading type press system, the billet is supplied by charging in the air, so maintenance of the centering precision of the billet loader becomes important and thus maintenance and control of the billet loader become necessary. Further, precision of the billet diameter, bending, end face, etc. is also required. Therefore, in practice, this is dealt with by enlarging the inside diameter of the container. However, increasing the inside diameter becomes a major cause of blisters in the product.
On the other hand, another system is, for example, proposed in Japanese Patent Publication (A) No. 4-231110, Japanese Patent Publication (A) No. 8-206727, etc. This system is a short stroke press system called the “rear loading type” as shown in FIG. 4. In this rear loading type, the stem is made to move horizontally or rise to secure the space for supplying the billet at the time of supplying the billet. By making the stem move in the horizontal direction or above from the initial position of the stem, a space for supplying the billet is formed at the stem side of the container at the side of or below the stem. A billet is supplied to this space.
However, in an extrusion press of the rear loading type short stroke press system, when employing the above-mentioned stem rising movement mechanism, the stem slide table supporting the stem vertically moves while sliding along the inside of a slide groove formed in the stem vertical movement support, so there was the problem of seizing between the liner applied to the slide groove and the stem slide table. When seizure occurred, it was necessary to stop the extrusion press and replace the liner. There was the problem that the facility was idled each time replacing the part.
Further, the stem slide table supports the heavy stem in a cantilever manner, so entire surface of the stem slide table does not uniformly slide with the liner of the slide groove. Therefore, a pushing force is created at particular parts of the top end and bottom end of the stem slide table. This uneven pushing force causes the stem slide table to easily partially wear down. For this reason, when the stem slide table is at the descent limit, the axis of the stem no longer matches with the axis X of the billet holding part of the container.
When in such a state, making the axis of the stem match the axis X of the billet holding part of the container is extremely difficult, so the stem slide table itself is replaced. This replacement leads to swelling costs. Further, the extrusion press facility must be stopped for the replacement. There were therefore the problem of the facility being idled and the problem of the work for centering the container and stem (work for matching the axis X) being troublesome and time consuming.
Therefore, the present invention has as its object the provision of a stem slide device eliminating slide rattling between a stem slide table to which a stem for pushing a billet loaded into a container is attached horizontally and a slide groove provided in a stem vertical movement support, preventing seizure between the stem slide table and stem vertical movement support, reducing the frequency of replacement of parts, simplifying the centering work, and enabling the stem to be raised at the time of supplying a billet.